1. Field of the Invention
This invention relates to printing apparatus, and more particularly to an ink recycling inking system for a rotary printing press wherein different ink colors are printed by a single plate cylinder.
2. Description of the Prior Art
In normal printing practice a single rotary plate cylinder is intended to print only a single ink color. For certain printing operations, e.g., in the printing of newspapers, it is often desired to apply ink in two or more different colors to a single plate cylinder at different positions along the axial length of the plate cylinder. For that purpose two or more doctor bars must be associated with the inking rollers and must be separated from each other so that ink of different colors can be applied to the inking roller in the desired portions and so that smearing or mixing of the different color inks will be avoided.
In German Patent Publication No. 1,224,327, there is disclosed an ink fountain which is intended for use in rotogravure printing machines and which includes separator walls to permit simultaneous printing with different color inks. The separator walls are spaced along the axis of the plate cylinder, and are in sliding contact with the periphery thereof. However, that structure does not include an ink fountain that is provided with two doctor blades, and the parts of the ink fountain that adjoin the separating wall and the highly elastic sealing bar provided on that wall are connected in a unit by means of screws, so that the separating wall cannot move relative to the adjoining doctor bars.
German Patent application Ser. No. 3,135,711 shows an ink recycling inking system that includes a doctor bar that has two doctor blades to define the walls of an ink chamber, but that is intended for applying ink of only a single color to an inking roller.
German Patent application Ser. No. 3,320,638 discloses an ink applying bar, which together with two doctor blades defines an ink trough and is divided by ink-separating plates into sections for different inks to be printed. The ink separating plates are guided in guide apertures in the ink applying bar, and are urged against a screen cylinder by means of leaf springs. However, if quick drying inks are employed, the movability of the ink separating plates can be adversely effected by ink that is drying in the guide apertures.
It is an object of the present invention to provide an ink recycling inking system that overcomes the shortcomings of the prior art identified above, and to provide an ink-recycling inking system that permits the application of printing inks of two or more different colors to a single plate cylinder at different positions along the axial length thereof without mixing of the inks.